Those 3 PHP questions

I have a question for you all. If you are asked to interview a candidate with 5 years of experience in PHP and you are allowed to ask only 3 theoretical questions and based on the answers of those 3 questions you have to select / reject the candidate. What would be those 3 questions?

Thanks & Regards

PS: Mods, if this is not the correct section pls move this thread to the appropriate one.